X-ray screening diaphragm



July 27, 1954 v s n' I 2,685,036

X-RAY SCREENING DIAPHRAGM Filed June 12, 1952 Patented July 27, 1954 UNITED STATES PATENT OFFICE X-RAY SCREENING DIAPHRAGM Edwin V. Smith, Yonkers, N. Y.

Application June 12, 1952, Serial No. 293,120

1 Claim. 1

This invention relates to a diaphragm or grid used in taking X-ray pictures or shadowgraphs of the anatomy or other objects of substantial thickness.

It is well known that when X-rays or other penetrating rays are passed through an object to be photographed, some of the rays are scattered or deflected from their original course. These scattered rays are known as secondary radiation. Such secondary radiation reaching the photographic film tends to fog or obscure the primary image.

To reduce this fogging, it has been a practice to interpose a grid or diaphragm known as a Bucky grid between the object and the film. This grid is made up of strips of lead or other X-ray opaque or impervious material separated by strips of X-ray transparent material, such as wood. The opaque strips serve to absorb secondary radiation approaching the film at an angle with respect to the plane of the opaque strips greater than the angle formed by a plane passing through the top edge of one strip and the bottom edge of the adjacent strip.

The amount of screening of secondary radiation obtained from such a grid therefore depends on the width of the spacing elements between the individual opaque strips and the thickness of the grid. This is known as the grid ratio. The greater the grid ratio, the better the screening of secondary radiation.

The object of this invention is to improve the screening effect of such grids towards secondary radiation without necessarily increasing the grid ratio. My invention makes it possible to improve such screening effect of a grid of given grid ratio.

In accordance with my invention there is located at the geometric center of the transparent spacing elements in the grid, a fine wire of X-ray opaque material, This wire will extend through the full length of the spacing element. This wire will serve to screen all secondary radiation passing through the geometric center of the grid at any angle to a plane passing through the wire parallel to the lead strips less than that formed by a plane passing through the center wire and the adjacent top and bottom edges of the opaque strips.

The wire used may be made of any dense material relatively opaque to X-rays or other such penetrating rays. For example, it may be made of lead, brass, tungsten, copper, silver, platinum, or the like. The thickness of such wire will depend upon the opacity to the penetrating rays, the width of the transparent spacing elements in which they are embedded and other factors. In general, the thinnest wire having maximum density which can be accurately embedded in 2 the geometric center of the spacing element should be the ideal toward which the grid fabricators should work.

For a better understanding of the invention, reference is now made to the accompanying drawing which is a greatly enlarged sectional view of a grid constructed according to the invention. Referring to the drawing, the reference character I designates the grid or diaphragm generally. This grid, or diaphragm, is made up with a series of spaced opaque strips 2 separated by X-ray transparent material 3. As illustrated, the grid is of the focal type with the individual opaque strips slanted to the focal point of the source of X-rays which is indicated generally at X so that the primary radiation tends to pass through the grid in a direction parallel to the opaque strips 2.

The spacing elements 3 may be made of any material permitting the free passage of the X- ray material and of sufficient mechanical strength to impart the desired rigidity to the grid. This material may be Celluloid, plastic, paper, wood or the like. As previously described, there is positioned in the geometric centers of the spacing elements an X-ray opaque wire 4. The position of this wire is located by the intersect of lines AB and CD. As previously mentioned, this wire serves to screen a substantial portion of secondary radiation passing through the spacing elements.

Having described the preferred embodiment of my invention, it will be understood that it embraces such other variations and modifications as I have included in the appended claim.

I claim:

In an X-ray diaphragm adapted to screen secondary radiation wherein said diaphragm is made up of strips of X-ray opaque material separated by spacing elements of X-ray transparent material, the improvement which comprises an X- ray opaque wire positioned in the geometric center of the spacing element and extending the full length thereof, having a diameter materially less than the width of said spacing elements.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,948,270 Liberson Feb. 20, 1934 2,141,193 Mott Dec. 27, 1938 2,195,729 Kamm Apr. 2, 1940 2,512,242 De Lassaus St. Genies June 20, 1950 FOREIGN PATENTS Number Country Date 453,447 Germany Dec. 10, 1927 

